and still others exhibit a progressive course (e.g., Guttmannova et al., 2011). This means that individuals may be classed together as reflecting the phenotype of interest at one point but actually reflect very different profiles when considered longitudinally. Taken together, the common problem is that dichotomous clinical diagnosis has manifold instances in which ‘apples and oranges’ may be combined and this creates a very heterogeneous and imprecise phenotype.
